Hi Ilias, On 2/18/24 11:03 PM, Ilias Apalodimas wrote: > On Thu, 15 Feb 2024 at 05:02, Kuppuswamy Sathyanarayanan > <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote: >> To allow event log info access after boot, EFI boot stub extracts >> the event log information and installs it in an EFI configuration >> table. Currently, EFI boot stub only supports installation of event >> log only for TPM 1.2 and TPM 2.0 protocols. Extend the same support >> for CC protocol. Since CC platform also uses TCG2 format, reuse TPM2 >> support code as much as possible. >> >> Link: https://uefi.org/specs/UEFI/2.10/38_Confidential_Computing.html#efi-cc-measurement-protocol [1] >> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> > [...] > >> +void efi_retrieve_eventlog(void) >> +{ >> + efi_physical_addr_t log_location = 0, log_last_entry = 0; >> + efi_guid_t cc_guid = EFI_CC_MEASUREMENT_PROTOCOL_GUID; >> + efi_guid_t tpm2_guid = EFI_TCG2_PROTOCOL_GUID; >> + int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2; >> + efi_tcg2_protocol_t *tpm2 = NULL; >> + efi_cc_protocol_t *cc = NULL; >> + efi_bool_t truncated; >> + efi_status_t status; >> + >> + status = efi_bs_call(locate_protocol, &tpm2_guid, NULL, (void **)&tpm2); >> + if (status == EFI_SUCCESS) { >> + status = efi_call_proto(tpm2, get_event_log, version, &log_location, >> + &log_last_entry, &truncated); >> + >> + if (status != EFI_SUCCESS || !log_location) { >> + version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2; >> + status = efi_call_proto(tpm2, get_event_log, version, >> + &log_location, &log_last_entry, >> + &truncated); >> + if (status != EFI_SUCCESS || !log_location) >> + return; >> + } >> + >> + efi_retrieve_tcg2_eventlog(version, log_location, log_last_entry, >> + truncated); >> + return; >> + } >> + >> + status = efi_bs_call(locate_protocol, &cc_guid, NULL, (void **)&cc); >> + if (status == EFI_SUCCESS) { >> + version = EFI_CC_EVENT_LOG_FORMAT_TCG_2; >> + status = efi_call_proto(cc, get_event_log, version, &log_location, >> + &log_last_entry, &truncated); >> + if (status != EFI_SUCCESS || !log_location) >> + return; >> + >> + efi_retrieve_tcg2_eventlog(version, log_location, log_last_entry, >> + truncated); >> + return; >> + } >> +} > [...] > > I haven't looked into CC measurements much, but do we always want to > prioritize the tcg2 protocol? IOW if you have firmware that implements > both, shouldn't we prefer the CC protocol for VMs? According the UEFI specification, sec "Conidential computing", if a firmware implements the TPM, then it should be used and CC interfaces should not be published. So I think we should check for TPM first, if it does not exist then try for CC. https://uefi.org/specs/UEFI/2.10/38_Confidential_Computing.html#confidential-computing > Thanks > /Ilias -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
